7i76e 5V home limit switch sensing

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04 Sep 2018 14:47 #117056 by jackdavies
Nearly have my machine setup, hopefully the last hurdle!

I am using 5v signal hall sensors for home/limit switches, but the input of my mesa 7i76e card has a minimum sense voltage of about 14v. What's the best way to boost the logic of the signal? Optocoupler?

I saw this post where it may be possible to use encoder inputs to sense the 5v? forum.linuxcnc.org/27-driver-boards/3041...itches-and-mesa-7i77

Thanks!

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04 Sep 2018 15:14 - 04 Sep 2018 15:14 #117059 by PCW
You could wire them to the expansion connector but these are only rated -0.5V to +7V and can be damaged by ground offsets that exceed the -0.5 V limit. If you add a 100 Ohm series resistor to the expansion I/O connections, there are ok from +7V to -5V though and much less liable to be damaged. You can use encoder inputs, but the 7I76E only has 3 and you may want to use the encoder.
Last edit: 04 Sep 2018 15:14 by PCW.
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